The blood-tumor capillary barrier to horseradish peroxidase permeability is being studied in three rat intracerebral glioma models (ASV, RG-2 and 9L), three rat subcutaneous glioma models (RG-2, 9L and S69) and human glioblastoma in nude mice. Dogs bearing ASV gliomas are being studied by CT and combined histological/histochemical methods. The goal is to characterize the differences among these models and to then use them appropriately for studies of the permeability, uptake and distribution of cancer chemotherapeutic agents. The cell kinetics of these models are being evaluated with four autoradiographic techniques: labeled mitoses, double labeling, continuous thymidine labeling and the stathmokinetic method. Tumor endothelium is being extracted for ultrastructural quantitation of fenestrations.